432 COSMOS. 



earth's crust, might, in my opinion, offer a greater appearance 

 of probability. It is not difficult to imagine that at the 

 margins of the up-heaving continents which now form the 

 more or less precipitous littoral boundary visible over the 

 surface of the sea, fissures have been produced by the simul- 

 taneous sinking of the adjoining bottom of the sea, through 

 which the communication with the molten interior is pro- 

 moted. On the ridge of the elevations, far from that area 

 of depression in the oceanic basin, the same occasion for 

 the existence of such rents does not exist. Volcanoes follow 

 the present sea-shore in single, sometimes double, and some- 

 times even triple parallel rows. These are connected by 

 short chains of mountains, raised on transverse fissures, and 

 forming mountain-nodes. The range nearest to the shore is 

 frequently (but by 110 means always) the most active, while 

 the more distant, those more in the interior of the country, 

 appear to be extinct or approaching extinction. It is some- 

 times thought that, in a particular direction in one and the 

 same range of volcanoes, an increase or diminution in the 

 frequency of the eruptions may be perceived, but the pheno- 

 mena of renewed activity after long intervals of rest render 

 this perception very uncertain. 



As many incorrect statements of the distance of volcanic 

 activity from the sea are circulated, either through ignorance 

 of, or inattention to, the exact localities both of the volcanoes 

 and of the nearest points of the coast, I shall here give the 

 following distances in geographical miles (each being equal 

 to about 2030 yards, or 60 to a degree) : In the Cordilleras 

 of Quito, the volcano of Sangay, which discharges uninter- 

 ruptedly, is situated in the most easterly direction, but its 

 distance from the sea is still 112 miles. Some very intelli- 

 gent monks attached to the mission of the Indies Andaquies 

 at the Alto Putumayo have assured me that on the upper 

 Rio de la Fragua, 41 a tributary of the Caqueta, to the eastward 

 of the Ceja, they had seen smoke issue from a conical moun- 



41 The position of the Volcan de la Fragua, as reduced at Timana, is 

 N. L. 1 48', long. 75 30' nearly. Compare the Carte Hypsometrique 

 des Nceuds de Montagnes dans les Cordilleres, in the large atlas of my 

 travels, 1831, pi. 5, see also pi. 22 and 24. This mountain, lying 

 isolated and so far to the east, ought to be visited by a geologist 

 capable of determining the longitude and latitude astronomically. 



